Problems putting pictures

OK as you can read at the title im having problem putting pictures on...
whats the difference between jpg and jpeg...?
cause mostly all my pictures are jpeg so i cant upload it here....
how can i always get the jpeg...?
then another problem...
i was putting a picture and its was BMP but it still doesnt work
it keep saying this
"Only JPG, PNG, GIF, BMP files are supported."
but im putting a BMP one...
and i really need the picture to show a friend of mine....
please help...!!!
i have been trying to figure it out since last year....
DX

....Even though you 'think' the file is 50kb, looks can be deceiving so check if it
really is below 250kb. (On the picture documents, hover on the pic and it'll show some
details about the pic....but I think you already know this. XD)

I believe jpeg is the Mac OS file extension, and jpg is the Windows extension (could
easily be wrong here, someone correct me) but if you're using Windows and you're bothered
then just put .jpg at the end of the filename when you save it. Although if you're using
one of the earlier versions of Paint, this'll make it pixellated.
BMPs are notorious for being huge mofo files. Open it up in your image editing program and
save as a jpg or my favourite, png. This should reduce the file size and if you're lucky,
allow you to upload the file now.